login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A280889 Number of set partitions of [2n] into exactly n blocks where sizes of distinct blocks are coprime. 1
1, 1, 4, 75, 56, 6930, 28512, 2849847, 972400, 693870606, 99936200, 63488350926, 475814969280, 166184959669300, 497980728000, 78877488833249175, 1489333512849120, 1116126129558913110, 1597083864660900000, 4467282986266589095530, 107279471180408841600 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..20.

Wikipedia, Coprime integers

Wikipedia, Partition of a set

FORMULA

a(n) = A280880(2n,n).

EXAMPLE

a(1) = 1: 12.

a(2) = 4: 123|4, 124|3, 134|2, 1|234.

a(4) = 56 = binomial(8,3): 12345|6|7|8, 12346|5|7|8, 12347|5|6|8, ..., 1|25678|3|4, 1|2|35678|4, 1|2|3|45678.

CROSSREFS

Cf. A280880.

Sequence in context: A000857 A240007 A046057 * A257367 A072373 A006412

Adjacent sequences:  A280886 A280887 A280888 * A280890 A280891 A280892

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jan 09 2017

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 13 03:46 EDT 2020. Contains 335673 sequences. (Running on oeis4.)